What is the correct way to implement THIS action into my Sprite-Kit Game?

I have a birdNode(spriteNode) traveling horizontally across a portrait scene.

The birdNode is dropping an egg(spriteNode) towards a cgPoint at the bottom of the screen.

I want the birdNode to randomely drop his egg at any time/position.

I have considered creating an NSTimeInterval with a random number between 2 seconds(time it takes birdNode to travel across screen), making the eggNode spawn at birdNode position, and invoking dropEgg function.

I have also considered generating a random CGPoint, loading the eggNode at

birdNode.position.x = randomPoint

and then invoking the dropEgg function.

My question is should I use a certain approach over another? Where exactly should I call the dropNode function. Right now i can not get it to work.

I have tried to consider randomTime/randomPosition in the currentTime update function below and drop the Node, but it makes eggs at every frame render so I don't think thats the right way.

override func update(currentTime: CFTimeInterval) {
}

Here is my code for dropping the egg, and creating a random dropPoint float, and bird flying across screen.

    func dropEgg(){

    //aim
    let dx = eggNodeTarget.position.x - birdNode.position.x
    let dy = eggNodeTarget.position.y - birdNode.position.y
    let angle = atan2(dy, dx)
    dragonProjectileNode.zRotation = angle

    //Seek
    var vx = turretNode.position.x
    var vy = turretNode.position.y

    //creates eggNodeSprite
    loadEggNode()  

    //shoot
    let shootAction = SKAction.moveTo(CGPointMake(vx, vy),duration: 0.75)
    eggNode.runAction(shootAction)

}

func loadRandDropLocationX() -> CGFloat{

    //or minNodeTimeValue?
    var MinNodeSpawnValue = self.frame.size.width * 0.2

    //or maxNodeTimeValue?
    var MaxNodeSpawnValue = self.frame.size.width * 0.8

    //or randomTime?
    var randomPointUInt32 = UInt32(MaxSpawnValue - MinSpawnValue)
    return (CGFloat(arc4random_uniform(randomPointUInt32)) + MinNodeSpawnValue)
}

func dragonMoveRight(){
    let moveDragon = SKAction.moveTo(loadRandDestinationRight(), duration: 2.3)
    dragonNode.runAction(moveDragon)
}